The ABO gene is located on chromosome 9, encoding proteins that form the basis of the ABO blood group system.
Research studies into pancreatic cancer, have shown that blood group A have a higher risk. The precise biological reasons as to why there is a relationship between ABO blood group and certain cancers are unknown, although two recent GWAS demonstrated that particular SNPs at the ABO locus were associated with the inflammatory cytokines tumor necrosis factor and intercellular adhesion molecule 1.
The ABO blood group is genetically-determined and therefore is not a modifiable risk factor as are cigarette smoking, body mass index, diet or other lifestyle-related variables. The risk of pancreatic cancer for individuals with blood group A has been replicated in several studies.
However, the risk of pancreatic cancer in individuals with blood group A (and likely B or AB) is nearly as strong as the risk of developing pancreatic cancer as a consequence of cigarette smoking; thus, the combination of multiple moderate risk factors (such as age and family history) could be used to calculate whether some individuals are at high enough risk to warrant counseling for risk reduction strategies or inclusion in pancreatic cancer screening trials.